Highly flexible sheeting and process of preparing the same



Patented May 22, 1934 HIGHLY FLEXIBLE SHEETING AND PROCESS or PREPARING THE SAME Carl J. MaIm, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New York No Drawing.' Application September 10, 1932,

Serial No. 632,561

22 Claims) (01. 18-57) 'I'hepresent invention relates to highly flexible sheeting prepared by coating out a skin' from a solution'of slightly hydrolyzed cellulose acetate propionate in a solvent consisting'of propylene chloride and a lower alcohol; particularlymethyl alcohol.

The preparation of sheets or 'skins of organic celluloseesters' coated out from acetone or the like is well-'known,' in fact most of th'e sheeting of that-nature which is employe'd for non-inflam mable photographic filmj' wrappingmaterial' etc. at the present timeis 'produced by coatingbut from acetone: solution? The" most commonerganic ester of cellulose employed is the acetate which usually must be hydrolyzed'to acetonesolubility' before use." In the case of a high grade cellulose acetate a skin'or sheet thereof, coated out from acetone, having 'a'thickness of approximately 005 in. may'exhibit an average flexibility of approximately 6 folds on a modified schopper fold-tester (the 'commo'nniethod of determining the flexibilities of sheets)-I -"However; this" flex 7 ibility is unusual and as a general-rule" the 'flex ibility of cellulose acetate fsheets coated from acetone is about 3:4 folds; '2 i One 'object of myinventionxisF to: prepare 'a' sheet or skin of an organic cellulose ester which has flexibility properties far above and beyon'd those exhibited by the organie'cellulose ester sheets which are employed-"commercially at the present time. Another object of my invention is to prepare a sheet or -skin ofan organ'iciester-of' cellulose which when unplasticized will exhibit flexibilities equal or superior to that exhibited by organic cellulose ester sheets or skins which'have been plasticizedw-Another 'object of -my inventionis to employ aslightlylrhydrolyzed cellulose acetate-propionate in-the preparation of sheets i which: are super-flexible; which ester has been foundto givel'non-flexible' sheets when-coated out Other objects will appear-herein.-

I have foundthat aslightly hydrolyzed cellu-' lose acetate-propionatehaving a propionyl con- I tent of at least-110%- (basedon the ester) andirrfrom acetone.

which at11east- /z :of 1% and not more than 6% of the combined. 'acyl-lcontent of the ester has been hydrolyzed off orreplaced-by hydroxyl groupsmay, when dissolved in a solvent oonsistingot propylene chloride [and a lower alcohoL-the formeruin predominating ;-proportions,- form sheets; or skins of surprisingly .high flexibil ity. I have found that the sheets-or skins-prepared in this manner exhibit .flexibilities, though the productsvare unplasticized, which are equal or superior to those of sheets of plasticizedorganicesters ofscellulose. have toundthat bymy invention, sheetszconsisting of slightly hydrolyzed. celluloseacetate-propionate alone have flexibilities higher than theiplasticized sheets con-- taining organieesters of cellulose known at the present time.

I have found that the addition of a plasticizer to my product does not markedly 'aifect its flexibility thus tending to show that the conditions induced by a plasticizer in the common run of cellulose ester pro-ducts are already present in my product without the necessity of diluting or adulterating the cellulose ester with an added plasticizer.

" My invention comprises the colloidizing of a slightly hydrolyzed cellulose acetate-propionate with a solvent consisting of propylene chloride and a lower alcohol, especially methyl alcohol,

the former being present in a predominating "amount. I have found that the solvent mixtures consisting of 70 to 90% propylene chloride and "the remainder of methyl alcohol are unusually effective in the preparation of sheets of great flexibility.

The following data illustrate the unusual results which are obtained by preparing sheets or skins according to my invention:'

A slightly hydrolyzed cellulose acetate-propionate-preparedby hydrolyzing for about 100 hours according to the disclosure of Malm and Fletcher-application Serial No. 551,546, flledJuly 17, 1931"and which contained about 15% pro pionyl and 26% acetyl (based on the ester) was coated'out in the form of a sheet from a propylene chloride-methyl alcohol solvent, in each different case varying the proportions of the two coniponents. The solution was madeup in the pro portion of 1 part of ester to'6v parts by weight of solvent. The resultsobtained were tabulated as follows:

Ratio propyl- Thickness of ene chloride sheet (thougagigigi to methyl sandths of an Bram alcohol inch) e It was desired to determine the effect of a plasticizer in increasing the flexibility of the sheets coated out by thepresent invention. The additional flexibility obtainedwhen a plasticizer was employed was not marked as illustrated by' The theory'might be advanced that the exceptional flexibility of the skins or sheets in my invention might be due to the presence of residual solvent in the skins which acts as a plasticizer therein. In order to determine the truth or falsity of that theory some of the skins of the preceding example were kept at a temperature of 100 degrees C. for 4 days, whereupon they were conditioned for 24 hours at a temperature of 20 C. and a relative humidity of 40%. The skin in the previous example which had been coated from the 90:10 propylene chloride-methyl alcohol solvent and containing no plasticizer exhibited after this conditioning treatment, a fold tolerance of 20-30 while the skin in that example coated from the same solvent but containing the triphenyl phosphate exhibited, after conditioning, an average fold tolerance of 25-35. The skin which had been coated from the :15 propylene chloridemethyl alcohol mixture after this treatment ex hibited an average fold tolerance of 25-35. It was to be expected that upon the conclusion of the severe drying conditions imposed upon the skin the flexibility would be less; however, this small decrease was about what would be expected from completely drying the skin and the results show that the residual solvent in the original skin plays but little part in the high flexibilities obtained in the present invention.

I have found that methyl alcohol gives the highest flexibilities when employed as the lower alcohol in our solvent mixture and it is preferred for use in this capacity; however, other lower alcohols may be employed to form sheets of high flexibility. Respective skins were coated from propylene chloride mixed with various lower alcohols and the following results were recorded:

In some cases in the above results the flexibility of the skin may be lower than it should be due to the skin not being stripped from the coating surface before it is completely cured. I have found that when cellulose derivative skins or sheets (especially of the organic esters of cellulose) are stripped from the coating surface before they are completely cured, the resulting skins exhibit a tolerance for many more folds than is the case with skins which are completely cured while on the coating surface.

The various advantages of the sheet or skin produced by my process over those which are employed at the present time are apparent. For example the sheets produced by my invention need not be plasticized to procure greatly superior flexibilities so that the reclamation of scrap sheeting which has been made by my process creates no problem of separating various materials to obtain the cellulose ester in pure form that is presented by the reclamation of cellulose esters whichwmust be plasticized to obtain sheets of satisfactory flexibility. Also there is no danger in the case of the sheets produced by my process of a decrease in flexibility of the sheets due to a loss of plasticizer as the flexibility is an inherent quality of the sheet produced according to my invention and not due to the addition of any added material. Y I

As was pointed out heretofore the term slight-- ly hydrolyzed cellulose acetate-propionate employed herein refers to a cellulose acetate-propionate having a propionyl content of at least 10% (based on the ester) and which has been hydrolyzed to a point that at least /2 of 1% and not more than 6% of the combined acyl content has been hydrolyzed off.

The sheets produced according to my process may be used in any instance where cellulose ester sheeting is employ-ed at the present time. Due to its high flexibiliti'es it is valuable for the man ufacture of photographic film and of thin sheeting, for wrapping purposes. These sheets due to their toughness are adapted for reinforcing materials especially those of a breakable nature such as paper, glass, wood as well as leather, metal, etc. My invention may also be employed for other purposes than making sheets or skins such as artificial silk manufacture, lacquering and overcoating in general, artificial leather, etc. Various other uses of the present invention will suggest themselves to those skilled in the art.

If desired, various'materials which are compatible may be added in the preparation of products according to my invention. For instance, triphenyl phosphate may be added to reduce inflammability. Although unnecessary, if the operator desires, he may add a known plasticizer, cellulose esters, resins or other comparable plastic materials to inpart to the resulting product the characteristics desired.

It will be seen that all of the sheets produced according to our invention in the above examples exhibited a fold tolerance of more than 8 folds and that the more flexible sheets exhibited a flexibility of at least 30. folds.

I claim as my invention:

1. The process which comprises colloidizing slightly'hydrolyzed cellulose acetate propionate with a solvent comprising a major proportion of propylene chloride and a minor proportion of a lower alcohol.

2. The process of preparing highly flexible sheeting which comprises dissolving a slightly hydrolyzed cellulose acetate-propionate in a propylene chloride-lower alcohol mixture in which the propylene chloride predominates, and depositing the resulting solution on a film-forming surface.

3. The process of preparing highly flexible sheeting which comprises dissolving a slightly hydrolyzed cellulose acetate-propionate in a propylene chloride-methyl alcohol mixture in which the propylene chloride predominates, and depositing the resulting solution on a filmforming surface.

4. The process of preparing highly flexible sheeting which comprises dissolving a slightly hydrolyzed cellulose acetate-propionate in a solvent mixture consisting of -70% propylene chloride and the remainder a lower alcohol, and depositing the resulting solution on a film-forming surface.

5. The process of preparing highly flexible sheeting which comprises dissolving a slightly hydrolyzed cellulose acetate-propionate in a solvent mixture consisting of 90-70% propylene chloride and the remainder methyl alcohol, and depositing the resulting solution on a film-forming surface.

6. The process of preparing highly flexible sheeting which comprises dissolving a slightly hydrolyzed cellulose acetate-propionate having a propionyl content of about 15% in a propylene chloride-lower alcohol mixture in which the propylene chloride predominates, and depositing the resulting solution on a film-forming surface.

'7. The process of preparing highly flexible sheeting which comprises dissolving a slightly hydrolyzed cellulose acetate-propionate having a propionyl content of about 15% in a propylene chloride-methyl alcohol mixture in which the propylene chloride predominates, and depositing the resulting solution on a film -forming surface.

8. A composition of matter comprising a slightly hydrolyzed cellulose acetate-proplonate dissolved in a solvent therefor comprising a major proportion of propylene chloride and a minor proportion of a lower alcohol.

9. A composition of matter comprising a slightly hydrolyzed cellulose acetate-propionate dissolved in a solvent therefor consisting of 90%- of propylene chloride and the remainder a lower alcohol.

10. A composition of matter comprising a slightly hydrolyzed cellulose acetate-propionate dissolved in a solvent therefor consisting of 90%-70% of propylene chloride and the remainder methyl alcohol.

11. A composition of matter comprising a slightly hydrolyzed cellulose acetate-propionate having a propionyl content of about 15% dissolved in a propylene chloride-alcohol mixture in which the propylene chloride predominates.

12. A composition of matter comprising a slightly hydrolyzed cellulose acetate-propionate having a propionyl content of about 15% dissolved in a solvent therefor consisting of 90% 70% of propylene chloride and the remainder methyl alcohol.

13. A highly flexible sheet resulting from the coating out of a slightly hydrolyzed cellulose acetate-propionate from its solution in a solvent comprising propylene chloride and a lower alcohol in which the propylene chloride predominates.

14. A highly flexible sheet resulting from the coating out of a slightly hydrolyzed cellulose acetate-propionate having a propionyl content of about 15% from its solution in a solvent comprising propylene chloride and a lower alcohol, the propylene chloride being present in a predominating proportion.

15. A highly flexible sheet resulting from the coating out of a slightly hydrolyzed cellulose acetate-propionate from its solution in a solvent comprising a propylene chloride and methyl alcohol in which the propylene chloride predominates.

16. A highly flexible sheet resulting from the coating out of a slightly hydrolyzed cellulose acetate-propionate having a propionyl content of about 15% from its solution in a solvent comprising propylene chloride and methyl alcohol, the propylene chloride being present in a predominating proportion.

17. A highly flexible sheet resulting from the coating out of a slightly hydrolyzed cellulose acetate-propionate from its solution in a solvent consisting of 70%-90% propylene chloride and the remainder of methyl alcohol.

18. A highly flexible sheet resulting from the coating out of a slightly hydrolyzed cellulose acetate-propionate having a propionyl content of about 15% from its solution in a solvent consisting of 70%90% propylene chloride and the remainder of methyl alcohol.

19. The process which comprises colloidizing a cellulose acetate propionate, which has a propionyl content of at least 10% and from which has been hydrolyzed off at least of 1% and not more than about 6% of the acyl content, with a solvent comprising a major proportion of propylene chloride and a minor proportion of a lower alcohol.

20. The process of preparing highly flexible sheeting which comprises dissolving a cellulose acetate propionate, which has a propionyl content of at least 10% and from which has been hydrolyzed oil at least of 1% and not more than about 6% or" the acyl content, in a solvent comprising a major proportion of propylene chloride and a minor proportion of a lower alcohol and depositing the resulting solution on a film-forming surface.

21. A composition of matter comprising a cellulose acetate propionate, which has a propionyl content of at least 10% and from which has been hydrolyzed off at least of 1% and not more than about 6% of the acyl content, dissolved in a solvent therefor comprising a major proportion of propylene chloride and a minor proportion of a lower alcohol.

22. A highly flexible sheet resulting from the coating out of a cellulose acetate propionate, which has a propionyl content of at least 10% and from which has been hydrolyzed off at least /2 of 1% and not more than about 6% of the acyl content, from its solution in a solvent comprising a major proportion of propylene chloride and a minor proportion of a lower alcohol.

CARL J. MALM. 

